They're pretty useless when it comes to your hunger bar as steak is more in numbers. And if you've ever noticed beef is dropped several more times and sometimes pigs drop no pork. Then when it comes to numbers, pigs are probably less and most of the time I find cows in packs and pigs wandering around in twos.
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If you (like me) don‘t want automated farms for XP, pigs are just as useful as other farm animals to gain XP. Just slaughter a bunch and then breed the remainder and all your mending stuff is repaired. Pig pens don‘t take up as much space as cattle pens and pigs are less annoying than chickens because even if you go near a chicken coop your inventory fills up with eggs. And pigs are cute.